1. Field of the Invention
The present invention relates to a method for evaluating reliability of a semiconductor device including a transistor.
2. Description of the Related Art
In recent years, metal oxides having semiconductor characteristics (hereinafter referred to as oxide semiconductors) have attracted attention. For example, a thin film transistor which includes a semiconductor layer using an amorphous oxide (an oxide semiconductor) whose electron carrier concentration is less than 1018/cm3 is disclosed in the Patent Documents 1 to 3.
When a transistor is applied to various products, the transistor preferably has high reliability. From this reason, characteristics of a transistor under various environments are needed to be recognized. For example, as a test for recognizing the characteristics of a transistor, a bias-temperature stress test (hereinafter referred to as a BT test) is known. Temperature, a bias condition, and the like are considered as test conditions of a BT test (see Patent Document 4).